Using the splitting middle term - the middle term of the general equation is divided in two such values that:

Product = a.c

For the given equation a = 3; b = 11 ;c = -4

= 3. - 4 = - 12

And either of their sum or difference = b

= 11

Thus the two terms are 12 and - 1

Difference = 12 - 1 = 11

Product = 12. - 1 = - 12

3x(x + 4)-1(x + 4) = 0

(x + 4)(3x-1) = 0

(x + 4) = 0 or (3x-1) = 0

x = -4 or x = 1/3

Roots of equation are - 4, 1/3